Wireless access provides tetherless access to mobile users, this has been done principally to address the requirements of two specific and disjoint domains: voice telephony and indoor data LANs. Cellular telephone networks have extended the domain of telephone service over a wireless last hop, while mobile-IP LANs such as WaveLAN and RangeLAN do the same for indoor users of TCP/IP data networks. Advances with wireless technology and high-speed integrated service wired networking promises to provide mobile users with comprehensive multimedia information access in the near future.
Personal Communication Services (PCS) are a broad range of individualized telecommunication services which enable individuals or devices to communicate irrespective of where they are at anytime. Personal Communication Networks (PCN) are a new type of wireless telephone system communicating via low-power antennas. PCNs offer a digital wireless alternative to the traditional wired line.
As a cellular mobile radio moves from one cell to another, it is "handed" off to the next cell by a controller, which determines which cell is receiving the strongest signal. Because the cellular user remains closer to the base transceiver than in classical mobile communications, the cellular user's transceiver requires less power and is therefore less expensive. The great advantage of the cellular concept over non-cellular radio is that higher capacity is allowed with the same frequency allocation. This advantage comes at a cost, the necessity of a large number of cell sites and associated radio ports.
Cellular and PCS technologies that are based on the North American Digital Cellular (NADC) use a spectrally efficient modulation technique called the .PI./4-DQPSK to satisfy the increasing demand for system capacity. The quality of the channel is related to the symbol error rate. Channel quality estimator based on eye-diagram is a popular technique, but this technique does not provide a number to determine the quality of the channel easily. In another technique, the known synchronization bits in the Time Division Multiple Access(TMDA) are used to estimate the number of errors. In this technique the Symbol Error Rate (SER) is calculated during the SYNC duration and not over the entire TDMA time slot.
Therefore, there is a need for a more reliable and rapid estimate of the channel quality.